U.S. patent number 11,009,297 [Application Number 14/687,640] was granted by the patent office on 2021-05-18 for fluidicially coupled heat pipes and method therefor.
This patent grant is currently assigned to WORLDVU SATELLITES LIMITED. The grantee listed for this patent is WorldVu Satellites Limited. Invention is credited to Armen Askijian, Daniel W. Field, James Grossman, Alexander D. Smith.
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United States Patent |
11,009,297 |
Smith , et al. |
May 18, 2021 |
Fluidicially coupled heat pipes and method therefor
Abstract
A passive thermal system for use in aerospace vehicles includes
a plurality of core-bearing radiator panels having at least one
heat pipe embedded therein. The portion of the heat pipe embedded
in each panel is fluidically coupled to the portions of the heat
pipe in the other core-bearing radiator panels.
Inventors: |
Smith; Alexander D. (San Jose,
CA), Askijian; Armen (Sunnyvale, CA), Field; Daniel
W. (Sunnyvale, CA), Grossman; James (Sunnyvale, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
WorldVu Satellites Limited |
Jersey |
N/A |
GB |
|
|
Assignee: |
WORLDVU SATELLITES LIMITED
(Jersey, GB)
|
Family
ID: |
1000005559773 |
Appl.
No.: |
14/687,640 |
Filed: |
April 15, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160305714 A1 |
Oct 20, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B23P
15/26 (20130101); F28D 15/02 (20130101); F28D
15/0233 (20130101); B64G 1/503 (20130101); B64G
1/506 (20130101); F28D 15/0275 (20130101); B64G
1/66 (20130101); B64G 1/1007 (20130101); B64G
1/443 (20130101); F28D 2015/0216 (20130101); B23P
2700/09 (20130101); F28D 2021/0021 (20130101) |
Current International
Class: |
F28D
15/02 (20060101); B64G 1/50 (20060101); B23P
15/26 (20060101); B64G 1/10 (20060101); F28D
21/00 (20060101); B64G 1/44 (20060101); B64G
1/66 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
2535276 |
|
Jul 2014 |
|
EP |
|
20110014856 |
|
Feb 2011 |
|
KR |
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WO-2014197695 |
|
Dec 2014 |
|
WO |
|
Other References
Authorized Officer: Blaine R. Copenheaver, "International Search
Report", dated Jul. 8, 2016 in counterpart International PCT
Application No. PCT/US2016/027685. cited by applicant .
Authorized Officer: Blaine R. Copenheaver, "Written Opinion of the
International Searching Authority", dated Jul. 8, 2016 in
counterpart International PCT Application No. PCT/US2016/027685.
cited by applicant.
|
Primary Examiner: Jones; Gordon A
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed:
1. An aerospace vehicle, wherein the aerospace vehicle includes a
passive thermal system, and wherein the passive thermal system
comprises: a first core-bearing radiator panel, a second
core-bearing radiator panel, and a third core-bearing radiator
panel, wherein the first core-bearing radiator panel and the third
core-bearing radiator panel are arranged opposite each other and
linked in part by the second core-bearing radiator panel, wherein
the first core-bearing radiator panel and the third core-bearing
radiator panel are in non-parallel planes, and the first
core-bearing radiator panel and the third core-bearing radiator
panel exhibit a structural divergence about a central axis of the
aerospace vehicle relative to each other being disposed in the
non-parallel planes in that the non-parallel planes tend to diverge
from each other in an earth-facing direction about the central axis
of the aerospace vehicle; and a first heat pipe, wherein a first
portion of the first heat pipe is disposed in the first
core-bearing radiator panel and a second portion of the first heat
pipe is disposed in the second core-bearing radiator panel, and
wherein the first and second portions of the first heat pipe are
fluidically coupled to one another.
2. The aerospace vehicle of claim 1, wherein the first heat pipe
has a first out-of-plane bend.
3. The aerospace vehicle of claim 2, wherein the first out-of-plane
bend is proximal to abutting edges of the first and second
core-bearing radiator panels.
4. The aerospace vehicle of claim 2, wherein the first out-of-plane
bend is characterized by a bend angle of at least 45 degrees.
5. The aerospace vehicle of claim 1, wherein the passive thermal
system further comprises a second heat pipe, wherein a first
portion of the second heat pipe is disposed in the first
core-bearing radiator panel, wherein a second portion of the second
heat pipe is disposed in the second core-bearing radiator panel,
and wherein the second portion of the second heat pipe is
configured to be longer than the second portion of the first heat
pipe in conformance with the structural divergence about the
central axis of the aerospace vehicle.
6. The aerospace vehicle of claim 5, wherein a third portion of the
first heat pipe is disposed in the third core-bearing radiator
panel, and wherein the first, the second, and the third portions of
the first heat pipe are fluidically coupled to one another.
7. The aerospace vehicle of claim 6, wherein the passive thermal
system further comprises a third heat pipe, wherein: (a) a first,
second, and third portion of the second heat pipe are disposed in
the first, the second, and the third core-bearing radiator panels,
respectively; (b) a first, second, and third portion of the third
heat pipe are disposed in the first, the second, and the third
core-bearing radiator panels, respectively; (c) the first, second,
and third portion of the second heat pipe are fluidically coupled;
and (d) the first, second, and third portion of the third heat pipe
are fluidically coupled.
8. The aerospace vehicle of claim 6, wherein the first heat pipe
has a second out-of-plane bend, wherein the second out-of-plane
bend is proximal to abutting edges of the second core-bearing
radiator panel and the third core-bearing radiator panel.
9. The aerospace vehicle of claim 8, wherein the first heat pipe
has a first out-of-plane bend, the first out-of-plane bend is
characterized by a first bend angle and the second out-of-plane
bend is characterized by a second bend angle, and wherein the first
bend angle and the second bend angle are the same as one
another.
10. The aerospace vehicle of claim 8, wherein the first heat pipe
has a first out-of-plane bend, the first out-of-plane bend is
characterized by a first bend angle and the second out-of-plane
bend is characterized by a second bend angle, and wherein the first
bend angle and the second bend angle are different from one
another.
11. The aerospace vehicle of claim 1, wherein the aerospace vehicle
is a satellite.
12. An aerospace vehicle having a passive thermal system as claimed
in claim 1, wherein: a third portion of the first heat pipe is
disposed in the third core-bearing radiator panel, and wherein the
first, second, and third portions of the first heat pipe are
fluidically coupled to one another.
13. The aerospace vehicle of claim 12, wherein the first heat pipe
has a first out-of-plane bend proximal to first abutting edges of
the first and second core-bearing radiator panels.
14. The aerospace vehicle of claim 13, wherein the first heat pipe
has a second out-of-plane bend proximal to second abutting edges of
the second and third core-bearing radiator panels.
15. The aerospace vehicle of claim 12, wherein the aerospace
vehicle is a satellite.
16. A method for forming a passive thermal system, wherein the
method comprises embedding a heat pipe in a first core-bearing
radiator panel and a second core-bearing radiator panel, said first
and second core-bearing radiator panels adopted to radiate heat to
an external environment, wherein the first core-bearing radiator
panel and the third core-bearing radiator panel are arranged
opposite each other and linked in part by the second core-bearing
radiator panel, wherein the first core-bearing radiator panel and
the third core-bearing radiator panel are in non-parallel planes,
and the first core-bearing radiator panel and the third
core-bearing radiator panel exhibit a structural divergence about a
central axis of the aerospace vehicle relative to each other being
disposed in the non-parallel planes in that the non-parallel planes
tend to diverge from each other in an earth-facing direction about
the central axis of the aerospace vehicle; wherein a first portion
of the heat pipe is embedded in the first core-bearing radiator
panel and a second portion of the heat pipe is embedded in the
second core-bearing radiator panel, and wherein the first portion
and the second portion of the heat pipe are fluidically coupled to
one another.
17. The method of claim 16, and further comprising positioning the
first and second core-bearing radiator panels in a final
orientation with respect to one another, the positioning resulting
in a first out-of-plane bend in the heat pipe proximal to abutting
edges of the first and second core-bearing radiator panels.
18. The method of claim 17, wherein positioning the first and
second core-bearing radiator panels in a final orientation
comprises partially rotating the first and second core-bearing
radiator panels with respect to one another in an amount of at
least 45 degrees, thereby resulting in a bend angle of at least 45
degrees for the first out-of-plane bend.
19. An aerospace vehicle, wherein the aerospace vehicle includes a
passive thermal system, and wherein the passive thermal system
comprises: a first core-bearing radiator panel, a second
core-bearing radiator panel, and a third core-bearing radiator
panel, wherein the first core-bearing radiator panel and the third
core-bearing radiator panel are arranged opposite each other and
linked in part by the second core-bearing radiator panel, wherein
the first core-bearing radiator panel and the third core-bearing
radiator panel are in non-parallel planes, and the first
core-bearing radiator panel and the third core-bearing radiator
panel exhibit a structural divergence about a central axis of the
aerospace vehicle relative to each other being disposed in the
non-parallel planes in that the non-parallel planes tend to diverge
from each other in an earth-facing direction about the central axis
of the aerospace vehicle; a first heat pipe; a solar panel; and a
y-bar coupled to the solar panel and configured to pass through a
y-bar opening in the first core-bearing radiator panel, wherein the
y-bar is configured to permit a rotation of the solar panel to
enhance exposure to sunlight.
20. The aerospace vehicle of claim 19, wherein the aerospace
vehicle further comprises: a lower panel configured to fit below
the second core-bearing radiator panel, wherein the lower panel is
of aero-space grade material; a battery module behind the lower
panel, wherein the solar panel is configured to charge the battery
module; and a motor; wherein the y-bar is further configured to
pass through a y-bar opening in the first core-bearing radiator
panel to the motor, wherein the y-bar is further configured to
permit the rotation of the solar panel by the motor to enhance the
exposure to sunlight, and wherein a first portion of the first heat
pipe is at a first elevation above the y-bar opening, and a second
portion of the first heat pipe is at the first elevation above the
lower panel.
21. The aerospace vehicle of claim 1, further comprising: a
plurality of payload antennas distributed on an external portion of
an earth-facing surface of the aerospace vehicle, wherein the
payload antennas are configured to provide a plurality of payload
signals to a plurality of user terminals.
22. The aerospace vehicle of claim 21, further comprising: a
plurality of reaction wheels distributed on an internal portion of
a space-facing surface, wherein the space-side surface is disposed
opposite to the earth-facing surface.
Description
FIELD OF THE INVENTION
The present invention relates to earth-orbiting communication
satellites.
BACKGROUND OF THE INVENTION
Communication satellites receive and transmit radio signals from
and to the surface of the Earth. Although Earth-orbiting
communications satellites have been in use for many years,
providing adequate cooling and heat distribution for the thermally
sensitive electronics components onboard such satellites continues
to be a problem.
There are two primary sources of heat with which a satellite's
thermal systems must contend. One source is solar radiation. Solar
radiation can be absorbed by thermal insulation shields or readily
reflected away from the satellite by providing the satellite with a
suitably reflective exterior surface. A second source of heat is
the electronics onboard the satellite. The removal of
electronics-generated heat is more problematic since such heat must
be collected from various locations within the satellite,
transported to a site at which it can be rejected from the
satellite, and then radiated into space.
Passive thermal panels can be used to dissipate heat from
satellites. In one configuration, the passive thermal panel
includes a honeycomb core having heat pipes embedded therein. A
heat pipe is a closed chamber, typically in the form of tube,
having an internal capillary structure which is filled with a
working fluid. The operating-temperature range of the satellite
sets the choice of working fluid; ammonia, ethane and propylene are
typical choices. Heat input (i.e., from heat-generating
electronics) causes the working fluid to evaporate. The evaporated
fluid carries the heat towards a colder heat-output section, where
heat is rejected as the fluid condenses. The rejected heat is
absorbed by the cooler surfaces of the heat-output section and then
radiated into space. The condensate returns to the heat input
section (near to heat-generating components) by capillary forces to
complete the cycle.
When two mechanically independent honeycomb panels need to be
thermally coupled, such as to move heat from one panel to the next,
an external "jumper" heat pipe or thermal strap is used. The jumper
or thermal strap bridges the heat pipes within the two panels via a
bolted interface. Because the heat pipe embedded within a given
panel is a self-contained structure, the thermal interface between
that heat pipe and another heat pipe is conduction only. In some
cases, a small part of an embedded heat pipe from one panel will
protrude therefrom and interface conductively with the embedded
heat pipe in the adjacent panel.
Because each of the thermal interfaces in the scenarios discussed
above is a conduction-only interface, a significant thermal
resistance is created to the flow of heat from panel to panel, even
when using state-of-the-art interface materials and techniques.
FIG. 4 depicts a method in the prior art for forming a passive
thermal system consisting of a several honeycomb radiator panels
and a plurality of heat pipes. In accordance with step 401 of
method 400, the heat pipes are formed. Suppose, for example, that
the passive thermal system is to have three radiator panels with
three heat pipes in each panel. As a consequence, a total of nine
heat pipes of appropriate length would be formed, typically via an
extrusion process. The heat pipes are then filled with fluid, such
as ammonia, per step 403.
In accordance with step 405, the heat pipes are next bent into
appropriate shapes, as dictated by the satellite design. For
example, there might be various holes in the radiator panels to
accommodate wires, rods, etc. that connect structures disposed on
the exterior of the satellite to internal components (e.g.,
processors, motors, etc.). Because each radiator panel has its own
captive heat pipes, all bends in the heat pipes are substantially
in plane (i.e., parallel to the radiator panel). Filling step 403
and bending step 405 can be performed in reverse order.
The heat pipes are then processed and tested, in known fashion, per
step 407. Assuming all the heat pipes pass the test protocol, they
are then embedded into the honeycomb radiator panels in accordance
with step 409. To continue with the example, three heat pipes would
be embedded in each of the three panels. Of course, to embed the
heat pipes, one of the two face sheets of metal that sandwich the
honeycomb interior of each radiator panel must remain off. And
passage ways through the honeycomb core must be formed to
accommodate the heat pipes. Care is required to ensure that at the
junction between radiator panels, the ends of the heat pipes in the
adjacent panels align with one another so that they can be
thermally coupled. This requires that each passage way through the
honeycomb core of each panel is in the correct location.
In step 411, the second face sheet is placed on each panel. And in
step 413, a film adhesive that is used to attach the second face
sheet to the honeycomb is cured, thereby completing each panel.
Finally, in step 415, the radiator panels are thermally coupled,
such as by using jumpers or thermal straps to thermally couple each
heat pipe in one of the panels to a respective heat pipe in the
adjacent radiator panel. As previously indicated, the jumpers or
thermal straps facilitate conductive heat transfer across the
interface of the heat pipes in adjacent panels. Step 415 is rather
labor intensive.
A need therefore remains for transporting heat from panel to panel
in satellites and other aeronautical applications.
SUMMARY OF THE INVENTION
The present invention provides an improved passive thermal system
wherein heat pipes in adjacent radiator panels are fluidically
coupled.
In accordance with the illustrative embodiment of the invention,
heat-pipe working fluid can flow freely between heat pipe segments
in adjacent core-bearing radiator panels (e.g., honeycomb core with
aluminum facesheets, etc.) of, for example, a satellite. This
completely eliminates the high thermal-resistance conductive
interface between adjacent panels in the prior art. Thermal
coupling from one side of, for example, a satellite, to the
opposite side is thus exceedingly efficient since a heat pipe is
typically nearly isothermal.
Forming a passive thermal system in accordance with the
illustrative embodiment requires very tight bend tolerances,
especially if the radiator panels have unusual orientations with
respect to one another. In a method in accordance with the present
teachings, heat pipes are embedded in all radiator panels that form
the passive thermal system prior to positioning the panels in their
final configuration. Once embedded, the panels are moved with
respect to one another, resulting in out-of-plane bends in the heat
pipes the abutting edges of adjacent radiator panels.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a satellite in accordance with the present
teachings.
FIG. 2 depicts an exploded view of portions of the satellite of
FIG. 1.
FIG. 3 depicts an embodiment of a passive thermal system for use in
conjunction with the satellite of FIGS. 1 and 2, in accordance with
the illustrative embodiment of the present invention.
FIG. 4 depicts a method in the prior art for embedding heat pipes
in a honeycomb radiator panel.
FIG. 5 depicts a method for creating the passive thermal system of
FIG. 3.
FIG. 6 depicts three honeycomb panels of the satellite of FIG.
1.
FIG. 7 depicts heat pipes for embedding into the panels of FIG.
6.
FIG. 8 depicts the heat pipes embedded in the panels of FIG. 6.
FIG. 9 depicts a cross-sectional view of honeycomb radiator panel
104 (with heat pipes embedded) in FIG. 8 along the line A-A in the
direction shown.
FIG. 10 depicts the completed passive thermal system resulting from
the partial rotation, out of plane, of the heat-pipe embedded
panels of FIG. 8.
DETAILED DESCRIPTION
Embodiments of the present invention can be used for all types of
satellites (e.g., LEO, GEO, etc.) and other aerospace vehicles, as
appropriate. Before addressing the specifics of the instant passive
thermal system, a satellite in which such a system can be used is
described.
Satellite.
FIG. 1 depicts satellite 100 in accordance with the present
teachings. FIG. 2 depicts an "exploded" view of some of the salient
features of satellite 100. Referring now to both FIGS. 1 and 2,
satellite 100 includes unified payload module 102, propulsion
module 114, payload antenna module 122, bus component module 132,
and solar-array system 140, arranged as shown. It is to be noted
that the orientation of satellite 100 in FIGS. 1 and 2 is "upside
down" in the sense that in use, antennas 124, which are facing "up"
in the figures, would be facing "down" toward Earth.
Unified payload module 102 comprises panels 104, 106, and 108. In
some embodiments, the panels are joined together using various
connectors, etc., in known fashion. Brace 109 provides structural
reinforcement for the connected panels.
Panels 104, 106, and 108 serve, among any other functionality, as
radiators to radiate heat from satellite 102. In some embodiments,
the panels include adaptations to facilitate heat removal. In some
embodiments, the panels comprise plural materials, such as a core
that is sandwiched by face sheets. Materials suitable for use for
the panels include those typically used in the aerospace industry.
For example, in some embodiments, the core comprises a lightweight
aluminum honeycomb and the face sheets comprise 6061-T6 aluminum,
which are bonded together, typically with an epoxy film
adhesive.
Propulsion module 114 is disposed on panel 112, which, in some
embodiments, is constructed in like manner as panels 104, 106, and
108 (e.g., aluminum honeycomb core and aluminum facesheets, etc.).
Panel 112, which is obscured in FIG. 1, abuts panels 104 and 106 of
unified payload module 102.
Propulsion module 114 includes fuel tank 116 and propulsion control
system 118. The propulsion control system controls, using one or
more valves (not depicted), release of propulsion gas through the
propulsion nozzle (not depicted) that is disposed on the
outward-facing surface of panel 114. Propulsion control system is
appropriately instrumented (i.e., software and hardware) to respond
to ground-based commands or commands generated onboard from the
control processor.
Payload antenna module 122 comprises a plurality of antennas 124.
In the illustrative embodiments, sixteen antennas 124 are arranged
in a 4.times.4 array. In some other embodiments, antennas 124 can
be organized in a different arrangement and/or a different number
of antennas can be used. Antennas 124 are supported by support web
120. In some embodiments, the support web is a curved panel
comprising carbon fiber, with a suitable number of openings (i.e.,
sixteen in the illustrative embodiment) for receiving and
supporting antennas 124.
In some embodiments, antennas 124 transmit in the K.sub.u band,
which is the 12 to 18 GHz portion of the electromagnetic spectrum.
In the illustrative embodiment, antennas 124 are configured as
exponential horns, which are often used for communications
satellites. Well known in the art, the horn antenna transmits radio
waves from (or collects them into) a waveguide, typically
implemented as a short rectangular or cylindrical metal tube, which
is closed at one end and flares into an open-ended horn (conical
shaped in the illustrative embodiment) at the other end. The
waveguide portion of each antenna 124 is obscured in FIG. 1. The
closed end of each antenna 124 couples to amplifier(s) (not
depicted in FIGS. 1 and 2; they are located on the interior surface
of panel 104 or 108).
Bus component module 132 is disposed on panel 130, which attaches
to the bottom (from the perspective of FIGS. 1 and 2) of the
unified payload module 102. Panel 130 can be constructed in like
manner as panels 104, 106, and 108 (e.g., aluminum honeycomb core
and aluminum facesheets, etc.). In some embodiments, panel 130 does
not include any specific adaptations for heat removal.
Module 132 includes main solar-array motor 134, four reaction
wheels 136, and main control processor 164. The reaction wheels
enable satellite 100 to rotate in space without using propellant,
via conservation of angular momentum. Each reaction wheel 136,
which includes a centrifugal mass (not depicted), is driven by an
associated drive motor (and control electronics) 138. As will be
appreciated by those skilled in the art, only three reaction wheels
136 are required to rotate satellite 100 in the x, y, and z
directions. The fourth reaction wheel serves as a spare. Such
reaction wheels are typically used for this purpose in
satellites.
Main control processor 164 processes commands received from the
ground and performs, autonomously, many of the functions of
satellite 100, including without limitation, attitude pointing
control, propulsion control, and power system control.
Solar-array system 140 includes solar panels 142A and 142B and
respective y-bars 148A and 148B. Each solar panel comprises a
plurality of solar cells (not depicted; they are disposed on the
obscured side of solar panels 142A and 142B) that convert sunlight
into electrical energy in known fashion. Each of the solar panels
includes motor 144 and passive rotary bearing 146; one of the y-bar
attaches to each solar panel at motor 144 and bearing 146. Motors
144 enable each of the solar panels to at least partially rotate
about axis A-A. This facilitates deploying solar panel 142A from
its stowed position parallel to and against panel 104 and deploying
solar panel 142B from its stowed position parallel to and against
panel 106. The motors 144 also function to appropriately angle
panels 142A and 142B for optimal sun exposure via the
aforementioned rotation about axis A-A.
Member 150 of each y-bar 148A and 148B extends through opening 152
in respective panels 104 and 106. Within unified payload module
102, members 150 connect to main solar-array motor 134, previously
referenced in conjunction with bus component module 132. The main
solar-array motor is capable of at least partially rotating each
member 150 about its axis, as shown. This is for the purpose of
angling solar panels 142A and 142B for optimal sun exposure. In
some embodiments, the members 150 can be rotated independently of
one another; in some other embodiments, members 150 rotate
together. Lock-and-release member 154 is used to couple and release
solar panel 142A to side panel 104 and solar panel 142B to side
panel 106. The lock-and-release member couples to opening 156 in
side panels 104 and 106.
Satellite 100 also includes panel 126, which fits "below" (from the
perspective of FIGS. 1 and 2) panel 108 of unified payload module
102. In some embodiments, panel 108 is a sheet of aerospace grade
material (e.g., 6061-T6 aluminum, etc.) Battery module 128 is
disposed on the interior-facing surface of panel 126. The battery
module supplies power for various energy consumers onboard
satellite 100. Battery module 128 is recharged from electricity
that is generated via solar panels 142A and 142B; the panels and
module 128 are electrically coupled for this purpose (the
electrical path between solar panels 142A/B and battery module 128
is not depicted in FIGS. 1 and 2).
Satellite 100 further includes omni-directional antenna 158 for
telemetry and ground-based command and control.
Disposed on panel 108 are two "gateway" antennas 160. The gateway
antennas send and receive user data to gateway stations on Earth.
The gateway stations are in communication with the Internet.
Antennas 160 are coupled to panel 108 by movable mounts 162, which
enable the antennas to be moved along two axes for optimum
positioning with ground-based antennas. Antennas 160 typically
transmit and receive in the K.sub.a band, which covers frequencies
in the range of 26.5 to 40 GHz.
Convertor modules 110, which are disposed on interior-facing
surface of panel 106, convert between K.sub.a radio frequencies and
K.sub.u radio frequencies. For example, convertor modules 110
convert the K.sub.a band uplink signals from gateway antennas 160
to K.sub.u band signals for downlink via antennas 124. Convertor
modules 110 also convert in the reverse direction; that is, K.sub.u
to K.sub.a.
In operation of satellite 100, data flows as follows for a data
request: (obtain data): requested data is obtained from the
Internet at a gateway station; (uplink): a data signal is
transmitted (K.sub.a band) via large, ground-based antennas to the
satellite's gateway antennas 160; (payload): the data signal is
amplified, routed to convertor modules 110 for conversion to
downlink (K.sub.u) band, and then amplified again; the payload
signal is routed to payload antennas 124; (downlink): antennas 124
transmit the amplified, frequency-converted signal to the user's
terminal.
When a user transmits (rather than requests) data, such as an
e-mail, the signal follows the same path but in the reverse
direction.
Passive Thermal System.
FIG. 3 depicts passive thermal system 300, which includes three
individual core-bearing (e.g., honeycomb, etc.) radiator panels,
such as panels 104, 108, and 106 of satellite 100 and four heat
pipes 370A, 370B, 370C, and 370D (collectively "heat pipes 370").
Each heat pipe runs through all three panels, such that fluid flows
uninterrupted through and between panels 104, 108, and 106. Thus,
the portion of a given heat pipe in a panel is fluidically coupled
to corresponding portions of the heat pipe in other panels that are
part of the same passive thermal system. Each heat pipe contains
heat-pipe fluid, typically ammonia, although other fluids may
suitably be used. The heat pipes are typically formed of
aluminum.
As used in this disclosure and the appended claims, the phrase
"core-bearing radiator panels" refers to radiator panels that
include a core material that is sandwiched by two face sheets. The
core material typically provides strength to the radiator panel,
while being a very lightweight structure. The face sheets are
typically selected for their ability to radiate and conduct heat.
This phrase also encompasses a panel that, while not including face
sheets, comprises a material that is suitably thick to accommodate
heat pipes therein. Panels made from, for example, solid metal,
would not be considered "core-bearing radiator panels," since solid
metal panels that are suitably thick to embed heat pipes would be
far too heavy for use in aerospace applications.
Heat pipes 370C and 370D bend "in-plane" (i.e., in the plane of the
radiator panel in which a portion thereof resides) to accommodate
the openings through panels 104 and 106. For example, in radiator
panel 106, heat pipe 370D has in-plane bend 372D and heat pipe 370C
has "in-plane" bend 372C. These two heat pipes have mirror image
in-plane bends in radiator panel 104. In some other embodiments,
the in-plane bends in radiator panels 104 and 106 are not mirror
imaged; rather, they differ to accommodate differences in certain
features (e.g., location of holes, add-on instrumentation, etc.) of
the two radiator panels.
Furthermore, all four heat pipes 370 also bend "out-of-plane"
(i.e., out of the plane of the radiator panel in which a portion
thereof resides) to accommodate the orientation of the panels with
respect to one another. For example, proximal to the abutting edges
of radiator panels 108 and 106, heat pipe 370A has out-of-plane
bend 374A, heat pipe 370B has out-of-plane bend 374B, heat pipe
370C has out-of-plane bend 374C, heat pipe 370D has out-of-plane
bend 374D. There are also four out-of-planes bends located proximal
to the abutting edges of radiator panels 104 and 108. These
out-of-of plane bends 374, at least in the context of heat pipes
embedded in radiator panels for use in satellites, are
unconventional.
The precise nature of each bend (i.e., the bend angle) is dictated
by the relative orientation of radiator panels with respect to one
another. For example, in passive thermal system 300, the
out-of-plane bend angle is about 90 degrees. In other embodiments,
the bend angle can be less or more than 90 degrees. This is a
function, in many embodiments, of the number of radiator panels
defining the exterior of the aerospace vehicle (e.g., satellite,
etc.). For example, since satellite 100 is more or less rectangular
and has four sides (neglecting a "top" and "bottom"), the radiator
panels are oriented at about 90 degrees with respect to one
another. In most embodiments, the bend angle of out-of-plane bends
will be at least 45 degrees.
As used in this disclosure and the appended claims, the phrase
"in-plane bend" or "bend in-plane," when used to refer to a bend in
a heat pipe, is to be referenced with respect to a "plane" defined
by a core-bearing radiator panel that contains a portion of the
heat pipe. Thus, if the panel is considered to extend in the X and
Y directions, thereby falling in an X-Y plane (ignoring panel
thickness), a bend in the heat pipe (as the heat pipe is oriented
in the panel) is "in plane" if it is parallel to the X-Y plane.
As used in this disclosure and the appended claims, the phrase
"out-of-plane bend" or "bend out-of-plane," when used to refer to a
bend in a heat pipe, is to be referenced with respect to a "plane"
defined by a core-bearing radiator panel that contains a portion of
the heat pipe. Thus, if the panel is considered to extend in the X
and Y directions, thereby falling in an X-Y plane (ignoring panel
thickness), a bend in the heat pipe (as the heat pipe is oriented
in the panel) is "out-of-plane" if it is not parallel to the X-Y
plane.
As used in this disclosure and the appended claims, the phrase
"bend angle," when used to refer to an out-of-plane bend in a heat
pipe, means the angle subtended by the two portions of the heat
pipe on either side of the out-of-plane bend.
FIG. 5 depicts method 500 for creating the passive thermal system
in accordance with the illustrative embodiment of the present
invention.
In accordance with step 501 of method 500, the heat pipes are
formed. Using passive thermal system 300 as an example, four heat
pipes (i.e., 370A, 370B, 370C, and 370D) are required for use with
three radiator panels 104, 106, and 108. By way of comparison, a
comparable prior-art arrangement would require, in addition to 3
radiator panels, 12 heat pipes and 8 jumpers/thermal straps.
Radiator panels 104, 106, and 108, which are part of satellite 100
shown in FIGS. 1 and 2, are depicted in FIG. 6. The four heat
pipes, with appropriate in-plane bends, are depicted in FIG. 7. The
heat pipes are formed via conventional processing, such as
extrusion. Like the prior-art method 400, after the heat pipes are
formed, they are filled with working fluid, such as ammonia, per
step 503.
In accordance with optional step 505, in-plane bends are formed in
one or more heat pipes, if such bends are required to accommodate
the configuration of the radiator panels. For example, heat pipes
370C and 370D require in-plane respective bends 372C and 372D so
the pipes can be routed past openings 156 and 152 (see FIG. 1).
In-plane bending is performed according to known techniques, such
as bender dies and mandrel inserts. As in prior-art method 400,
filling step 503 and bending step 505 can be performed in reverse
order.
Heat pipes 370 are then embedded into all the core-bearing radiator
panels in a particular passive thermal system (i.e., 3 panels in
the case of passive thermal system 300) in accordance with step
507. To accomplish this, the panels are laid flat, side-by-side. As
discussed in conjunction with prior-art method 400, to embed the
heat pipes, one of the two face sheets of metal that sandwich the
core of each radiator panel must remain off. Appropriate portions
of the core material in each of the panels are removed to
accommodate the heat pipes. At this point in the method, the
radiator panels and the heat pipes are in a planar
configuration.
FIG. 8 depicts heat pipes 370 embedded in radiator panels 104, 108,
and 106. FIG. 9 depicts a cross-sectional view of panel 104 along
the line A-A in the direction shown.
In step 509, the second face sheet is placed on each core-bearing
radiator panel. In step 511, a film adhesive that is used to attach
the second face sheet to the core is cured, thereby completing each
panel.
In accordance with embodiments of the present invention, and unlike
the prior art, core-bearing radiator panels 104, 108, and 106 are
moved (i.e., partially rotated) into their final "use"
configuration with respect to one another. With continuing
reference to FIG. 8, panel 104 is partially rotated about axis B-B
in the direction of the arrows (i.e., forward "out-of-the-page").
Similarly, panel 106 is partially rotated about axis C-C in the
direction of the arrows (i.e., forward "out-of-the-page"). This
creates, per step 513, out-of-plane bends in all of the heat pipes
at the abutting edges of the three panels.
Referencing FIG. 3, at the abutting edges of panels 108 and 106
are: out-of-plane bend 374A (heat pipe 370A), out-of-plane bend
374B (heat pipe 370B), out-of-plane bend 374C (heat pipe 370C), and
out-of-plane bend 374D (heat pipe 370D). There are another four
out-of-plane bends at the abutting edges of panels 104 and 106. In
step 515, the heat pipes are then processed and tested, in known
fashion.
FIG. 10 depicts a completed passive thermal system, such as results
from rotating, out-of-plane, the heat-pipe-embedded panels of FIG.
8. Out-of-plane bends of heat pipes 370A, 370B, 370C, and 370D are
visible at the abutting edges of panels 104 and 108.
It is to be understood that the disclosure describes a few
embodiments and that many variations of the invention can easily be
devised by those skilled in the art after reading this disclosure
and that the scope of the present invention is to be determined by
the following claims.
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